基于USLE模型的长株潭城市群生态绿心区水土流失研究

[目的]研究2018年长株潭(长沙市—株州市—湘潭市)城市群生态绿心区最佳植被覆盖和水土流失状况,为区域综合治理提供理论依据。[方法]运用GIS和RS技术,以长株潭区域降雨、土壤、地形、土地利用等数据为基础,采用归一化植被指数(NDVI)模型和USLE国际通用土壤流失方程为优选模型。[结果]长株潭绿心区总面积为52 287 hm~2,整体植被状况较好,高覆盖度(75%～100%)面积最大,占绿心区总面积一半以上,为26 598.40 hm~2;中低覆盖度(30%～40%)面积最小,占区域总面积的8.61%,为4 501.91 hm~2。长株潭城市群生态绿心区总侵蚀(不含微度)面积为3 654.24 hm~2,占总面积的6.99%。湘潭市侵蚀比重最高,为8.51%,长沙市次之,为6.67%,株洲市侵蚀总比例最小,为5.68%。工程建设用地在禁止开发区、限制开发区和控制建设区的侵蚀面积分别为963.92,310.74,735.11 hm~2。[结论]受人为因素、城市建设、产业分布等影响,长株潭城市群生态绿心区覆盖度空间呈现西部低,中东部高的格局,工程建设是造成绿心区土壤侵蚀的主要原因。     

Sap flow characteristics and physiological adjustments of two dominant tree species in pure and mixed plantations in the semi-arid Loess Plateau of China

It is essential to understand the water consumption characteristics and physiological adjustments of tree species under drought conditions, as well as the effects of pure and mixed plantations on these characteristics in semi-arid regions. In this study, the normalized sap flow (SF_n), leaf water potential, stomatal conductance (g_s), and photosynthetic rate (P_r) were monitored for two dominant species, i.e., Pinus tabuliformis and Hippophae rhamnoides, in both pure and mixed plantations in a semi-arid region of Chinese Loess Plateau. A threshold-delay model showed that the lower rainfall thresholds (R^L) for P. tabuliformis and H. rhamnoides in pure plantations were 9.6 and 11.0 mm, respectively, and the time lags (τ) after rainfall were 1.15 and 1.76 d for corresponding species, respectively. The results indicated that P. tabuliformis was more sensitive to rainfall pulse than H. rhamnoides. In addition, strong stomatal control allowed P. tabuliformis to experience low g_s and P_r in response to drought, while maintaining a high midday leaf water potential (Ψ_m). However, H. rhamnoides maintained high g_s and P_r at a low Ψ_m expense. Therefore, P. tabuliformis and H. rhamnoides can be considered as isohydric and anisohydric species, respectively. In mixed plantation, the values of R^L for P. tabuliformis and H. rhamnoides were 6.5 and 8.9 mm, respectively; and the values of τ were 0.86 and 1.61 d for corresponding species, respectively, which implied that mixed afforestation enhanced the rainfall pulse sensitivity for both two species, especially for P. tabuliformis. In addition, mixed afforestation significantly reduced SF_n, g_s, and P_r for P. tabuliformis (P<0.05), while maintaining a high leaf water potential status. However, no significant effect of mixed afforestation of H. rhamnoides was observed at the expense of leaf water potential status in response to drought. Although inconsistent physiological responses were adopted by these species, the altered water consumption characteristics, especially for P. tabuliformis indicated that the mixed afforestation requires further investigation.     

基于不同有效积温的玉米干物质累积量模拟

为获得研究区适宜的玉米干物质累积量(DM)估算模型,通过2017—2019年在吉林省长春地区开展的3年农田试验,观测玉米生育期内作物根区20 cm地温、40 cm地温、农田气温、作物冠层温度以及玉米地上部干物质累积量等数据,建立基于不同有效积温的Logistic模型及其归一化模型,并用实测数据进行模型验证。结果表明,基于有效积温建立的Logistic模型可以模拟单株玉米干物质累积量生长,但不同地点、不同年份所建立的模型参数差异较大;Logistic归一化模型能够很好地模拟区域玉米干物质增长,在利用实测数据进行模型验证中,基于作物根区20 cm地温、40 cm地温、农田气温和作物冠层温度4种类型有效积温的Logistic归一化模型,其均方根误差、相对误差、决定系数和模型一致性系数都能达到较优值;以2019年数据建立的Logistic归一化模型对玉米干物质累积量模拟效果最优;基于有效冠层积温的Logistic归一化模型模拟效果较优。本研究结果可为灌区精量灌溉决策和管理提供技术支撑。     

基于Landsat影像稀疏植被斑块格局对降水响应

【目的】古尔班通古特沙漠稀疏植被斑块格局是水分稀缺的荒漠区对降水在地表的表现。【方法】基于年降水量变化特征,选择1990年TM影像、2001年ETM+、2010年TM影像和2015年OLI遥感影像为数据源,结合1990~2015年蔡家湖气象站逐年的降水数据,计算古尔班通古特沙漠南缘的植被盖度、斑块面积、斑块数量、斑块密度,分析不同植被盖度、面积变化趋势,探讨年降水量对植被盖度、斑块面积、数量、密度的影响。【结果】1990~2015年,植被盖度总体呈减少趋势,其中二级植被面积明显增加(1 089.557 km²),增幅为20.154%,一、三、四级植被面积略有减少,减幅分别为-98.752%、-61.581%、-96.889%。随着降水量的增加,斑块数量,密度增加,破碎程度变小,植被盖度增加。【结论】1990~2015年古尔班通古特沙漠南缘稀疏植被盖度随年降水的变化总体呈退化-好转-退化趋势。年降水量变化与稀疏植被盖度、斑块面积、数量、密度均呈正相关关系。     

1999-2016年天山西部植被覆盖的时空变化

[目的]调查天山西部生态环境植被覆盖状况,为科学保护区域生态环境和管理提供科学依据。[方法]以天山西部林区—霍城林场为研究对象,基于1999,2007和2016年3个时期的Landsat TM遥感影像和DEM数据,运用归一化植被指数分析研究区植被覆盖情况和空时变化特征。[结果]时间变化上,1999—2016年期间霍城林场植被覆盖以Ⅱ和Ⅲ级为主,所占比重达到55%以上,总体上是呈现上升趋势;空间分布上,霍城林场因海拔、坡度和坡向等地形因子的不同而出现不同的分布和变化特征,当海拔在1 500~2 000 m和2 000~2 500 m或者坡度30°~45°的区域时,植被覆盖度相对较高;当海拔 < 1 500 m以及 > 2 500 m或坡度 < 30°的区域时,植被覆盖度相对较低;植被覆盖度随着坡向的变化而变化着,呈现出阴坡 > 半阴坡 > 半阳坡 > 阳坡的分布特征;当海拔 < 1 500m和坡度 < 30°的区域时,植被覆盖度变化较为明显,而当海拔 > 2 500 m和坡度 > 45°的区域时,因受人为社会活动影响小,植被覆盖变化不明显。[结论]1999—2016年期间,霍城林场植被覆盖在时间变化上总体呈现上升趋势,在空间分布上因海拔、坡度和坡向等地形因子的不同呈现不同的分布和变化特征。     

台湾省植被NDVI随海拔高度的变化及其气候响应

[目的]揭示台湾省陆地植被生态系统随海拔高度的变化趋势及其响应程度,为区域可持续发展、生态环境保护提供理论依据。[方法]基于台湾省1998—2018年SPOT/VEGETATION NDVI卫星遥感数据、气象及DEM数据,结合相关分析法、回归分析法等数理统计方法,对气候变化下的台湾省植被归一化植被指数(NDVI)变化趋势及区域响应进行了分析。[结果] 1998—2018年台湾省植被NDVI均值增长率为5.09%;台湾省不同高程范围所占的面积比例差异较大,500 m区域的面积比例高达52.49%,3 600 m区域的面积比例仅为0.01%,且NDVI均呈现较低值,分别为0.72和0.73;1998—2018年台湾省海拔除3 600 m外,其他海拔高程范围NDVI均值增长明显(p0.001);在500～3 600 m高程范围内,NDVI年均值与气温、降雨相关关系显著(p0.05)。[结论]海拔越高,植被生长状况对降雨的变化较气温更为敏感。     

Improving in-season nitrogen recommendations for maize using an active sensor

An active crop canopy reflectance sensor could be used to increase N-use efficiency in maize (Zea mays L.), if temporal and spatial variability in soil N availability and plant demand are adequately accounted for with an in-season N application. Our objective was to evaluate the success of using an active canopy sensor for developing maize N recommendations. This study was conducted in 21 farmers’ fields from 2007 to 2009, representing the maize production regions of east central and southeastern Pennsylvania, USA. Four blocks at each site included seven sidedress N rates (0–280 kg N ha⁻¹) and one at-planting N rate of 280 kg N ha⁻¹. Canopy reflectance in the 590 nm and 880 nm wavelengths, soil samples, chlorophyll meter (SPAD) measurements and above-ground biomass were collected at the 6th–7th-leaf growth stage (V6–V7). Relative amber normalized difference vegetative index (ANDVI_relative) and relative SPAD (SPAD_relative) were determined based on the relative measurements from the zero sidedress treatment to the 280 kg N ha⁻¹ at-planting treatment. Observations from the current study were compared to relationships between economic optimum N rate (EONR) and ANDVI_relative, presidedress NO₃ test (PSNT), or SPAD_relative that were developed from a previous study. These comparisons were based on an absolute mean difference (AMD) between observed EONR and the previously determined predicted relationships. The AMD for the relationship between EONR and ANDVI_relative in the current study was 46 kg N ha⁻¹. Neither the PSNT (AMD = 66 kg N ha⁻¹) nor the SPAD_relative (AMD = 72 kg N ha⁻¹) provided as good an indicator of EONR. When using all the observations from the two studies for the relationships between EONR and the various measurements, ANDVI_relative (R² = 0.65) provided a better estimate of EONR than PSNT (R² = 0.49) or SPAD_relative (not significant). Crop reflectance captured similar information as the PSNT and SPAD_relative, as reflected in strong relationships (R² > 0.60) among these variables. Crop canopy reflectance using an active sensor (i.e. ANDVI_relative) provided as good or better an indicator of EONR than PSNT or SPAD_relative, and provides an opportunity to easily adjust in-season N applications spatially.     

基于混合像元分解的香格里拉市高山松空间分布变化研究

利用香格里拉市1997-2017年每5 a的Landsat遥感影像、2018年外业调查数据、森林资源二类调查数据和DEM数据为数据源,以高山松为对象,综合运用混合像元分解技术、决策树分类和GIS技术对其空间分布变化进行分析。结果表明,1）分类中,高山松归一化多分量指数阈值为0.333,云南松归一化多分量指数阈值为0.208;云冷杉归一化多分量指数阈值为0.362。2）各年分类结果总体精度分别为69.42%、76.73%、81.07%、78.90%和76.53%。3）香格里拉市高山松覆盖面积2002年比1997年减少了13.40%,2007年比2002年减少了2.47%,2012年比2007增加了8.96%,2017年比2012年增加了4.06%,呈现出先减少后增加的趋势。4）研究区内高山松主要分布在海拔高度2 800~3 800 m,1 800~2 800 m高山松面积总体呈现为轻微下降趋势;2 800~3 300 m海拔区间1997-2007年呈现下降趋势,2007-2017年呈现上升趋势,3 300~3 800 m区间内1997-2002年高山松面积呈现下降趋势,2002-2017年高山松面积逐年上升,3 800~4 800 m区间内1997-2017年高山松面积逐年下降。利用混合像元分解构建归一化多分量指数结合决策树分类对树种分类具有一定的参考价值,高山松时空变化结果对森林资源管理和后续研究可提供科学数据支撑。     

Multi-Temporal Detection of Rice Phenological Stages Using Canopy Spectrum

Information on rice phenology is essential for yield estimation and crop management. To test the ability of remote sensing in detecting multiple phenological stages, paddy rice canopy spectrum was measured by a hand-held radiometer. Normalized difference vegetation index(NDVI) was calculated from spectrum, and the slope of NDVI was obtained as its difference. We evaluated the response of NDVI and its slope to rice growth with a comparison of two late-season rice cultivars. The results showed that NDVI and its slope curves had distinct variation corresponding to rice development and they could be used as cultivar-independent phenological indicators. The dates of flooding and transplanting, tillering, panicle development, heading and flowering, maturity, harvest stages, and even field management practices, could be deduced from these indicators. ‘NDVI ≤ 0' could be used as a single threshold for the detection of flooding and transplanting. The largest spike in the curve of the NDVI slope indicated the duration of tillering stage. The next spike corresponded to panicle development. The heading and flowering stage was characterized by the maximum NDVI and the change of NDVI slope from positive to negative. At the maturity stage, NDVI decreased continuously, and its slope fluctuated just below zero. When rice grains were completely mature and ready for harvest, NDVI decline was accelerated. At harvest, NDVI slope reached its minimum value. The distinction between heading and maturity stages was obscure, most likely due to NDVI saturation at high biomass. The study might provide references for paddy rice phenology determination through remote sensing images.     

Analysis of Cleanroom Technology Through Angle of Design

During the implementation of Cleanroom Model, there are a lot of particular problems need to be resolved, which make it indispensable to grasp the essence and the principles of CRM. The article is on the essential research work in the design procedure of the Cleanroom technology. Through the analysis, it proposes a general architecture, based on which the entry point of the solving process and the distribution of the reducing procedure are introduced.